Having a issue while using extend audio

[shayankar10]

Trying the extend audio in test environment. but everytime it is having a issue like:
{
"error": "Internal server error: "Unauthorized""
}

here giving the payload as well:

{
"audio_id": "90d607ef-f6ae-4535-9f03-2bdac14e30be",
"prompt": "[Verse]\nFields of red in dawn's cruel light\nRuins whisper in the dead of night\nEchoes of our lost refrain\nMemories bound in chains of pain\n\n[Verse 2]\nHeroes gone and shadows cast\nEmpty homes and futures past\nSilent cries beneath the stars\nWounded hearts and broken scars\n\n[Chorus]\nIn the silence after thunder\nShattered dreams we sit and wonder\nWho we are and what we've lost\nEvery victory comes with cost\n\n[Bridge]\nTattered flags and broken shields\nGhosts of glory haunt these fields\nSongs of sorrow fill the air\nEmpty promises everywhere\n\n[Verse 3]\nWhere the laughter used to ring\nNow despair is haunting everything\nEmpty chairs around the fire\nHope's reflection turning dire\n\n[Chorus]\nIn the silence after thunder\nShattered dreams we sit and wonder\nWho we are and what we've lost\nEvery victory comes with cost",
"continue_at": 240,
"title": "Echoes of the Fallen",
"tags": "eavy metal slow melodic"
}

Can you explained me why it is happening